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publications:1996macromolslippage [2011/12/17 20:05] cgay |
publications:1996macromolslippage [2016/01/19 11:06] (Version actuelle) cgay |
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[[http://pubs.acs.org/doi/abs/10.1021/ma950753j|Journal link]] - | [[http://pubs.acs.org/doi/abs/10.1021/ma950753j|Journal link]] - | ||

[[publications:bibtex|BibTeX]] - | [[publications:bibtex|BibTeX]] - | ||

- | DOI:10.1021/ma950753j | + | [[http://dx.doi.org/10.1021/ma950753j|DOI:10.1021/ma950753j]] |

**Abstract / Résumé** | **Abstract / Résumé** | ||

We study the slippage of a highly viscous polymer melt (P monomers per chain) on a solid substrate grafted by a few smaller chains in the mushroom regime (N monomers per chain, grafting density nu). The friction is provided by the sliding motion of the P chains of the "skin" (thickness Rp=P^{1/2}a) which are entangled with the tethered chains. At low grafting densities, only a fraction of the P chains in the skin are coupled to the N chains, and the friction on the mushrooms is additive. Above a threshold nuc, all P chains of the skin are trapped, and the low-velocity friction becomes independent of the grafting density. Above a certain threshold slippage velocity V*(nu), the N chains are strongly stretched and reach the "marginal state", corresponding to a constant shear stress. We expect that for nu > nuc, V*(nu) increases linearly. Depending on N, P, nu and V, we predict a cascade of regimes, where the N chains may be ideal, stretched, or "marginal", while the trapped chains may be ideal or stretched and progressively disentangle from the N chains. | We study the slippage of a highly viscous polymer melt (P monomers per chain) on a solid substrate grafted by a few smaller chains in the mushroom regime (N monomers per chain, grafting density nu). The friction is provided by the sliding motion of the P chains of the "skin" (thickness Rp=P^{1/2}a) which are entangled with the tethered chains. At low grafting densities, only a fraction of the P chains in the skin are coupled to the N chains, and the friction on the mushrooms is additive. Above a threshold nuc, all P chains of the skin are trapped, and the low-velocity friction becomes independent of the grafting density. Above a certain threshold slippage velocity V*(nu), the N chains are strongly stretched and reach the "marginal state", corresponding to a constant shear stress. We expect that for nu > nuc, V*(nu) increases linearly. Depending on N, P, nu and V, we predict a cascade of regimes, where the N chains may be ideal, stretched, or "marginal", while the trapped chains may be ideal or stretched and progressively disentangle from the N chains. |